Hi, similar to before what are the messages you have sent from your arduino? Can you capture them in the monitor. They should look like:
{UI|SET|MyTrackbar.Value=10}
{UI|SET|MyTrackbar.Value=20}
{UI|SET|MyTrackbar.Value=30}
{UI|SET|MyTrackbar.Value=40}
{UI|SET|MyTrackbar.Value=50}